The present invention relates to an infrared and ultraviolet radiation absorbing glass having a green tint. More particularly, it relates to an infrared and ultraviolet radiation absorbing glass having high transmission and pale bluish green tint which is suitable for use as a glass for automobiles or a glass for construction.
In recent years, interior trim of automobiles tends to be luxury, and from the standpoint of the demand to protect the interior trim from deterioration and reduce load of air conditioning, a green-tined glass having infrared and ultraviolet radiation absorbing power imparted thereto has been proposed as window glass of automobiles.
For example, JP-A-4-310539 (the term xe2x80x9cJP-Axe2x80x9d used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d) discloses an infrared and ultraviolet radiation absorbing glass consisting essentially of, in % by weight, 65-75% SiO2, 0.1-5% Al2O3, 10-18%Na2O, 0-5%K2O, 5-15% CaO, 1-6% MgO and 0.05-1.0% SO3, and having incorporated therein as coloring components, 0.5-1.2% total iron oxide in terms of Fe2O3, 0.1-3.0% CeO2 and 0-1.0% TiO2, wherein 20-40% of the total iron oxide in terms of Fe2O3 is FeO.
JP-A-5-78147 discloses an infrared and ultraviolet radiation absorbing glass as a glass having relatively pale green tint in various infrared and ultraviolet radiation absorbing glasses. This glass comprises, in % by weight, basic components comprising 68-72% SiO2, 1.6-3.0 Al2O3, 8.5-11.0% CaO, 2.0-4.2% MgO, 12.0-16.0% Na2O, 0.5-3.0% K2O and 0.5-3.0% SO3, and coloring components comprising 0.58-0.65% total iron oxide in terms of Fe2O3, 0.1-0.5% CeO2, 0.1-0.4% TiO2 and 10-350 ppm MnO as a trace oxide.
JP-A-6-56466 discloses a glass having low total solar energy transmission and ultraviolet transmission. This glass comprises, in % by weight, a soda-lime-silica basic glass, and having incorporated therein 0.53-0.70% total iron oxide in terms of Fe2O3, 0.35-0.50% Fe2O3, 0.16-0.24% FeO, 0.2-0.4% TiO2, and 0.5-0.8% total cerium in terms of CeO2, wherein an amount of FeO in terms of Fe2O3 is 30-40% based on the weight of the total iron oxide in terms of Fe2O3.
In the infrared and ultraviolet radiation absorbing glass disclosed in the above-described JP-A-4-310539, the coloring components are preferably 0.7-1.0% total iron oxide in terms of Fe2O3, and 0.3-2.0 CeO2, and a visible light transmission when the glass has a thickness of 5 mm is 66.1-66.8% as shown in the examples. As is understood from this, a green tint of the glass is comparatively dark. However, in some cases such a dark tint may not be preferred as a glass for automobiles, or is not generally preferred as a glass for construction.
In the infrared and ultraviolet radiation absorbing glass disclosed in the above-described JP-A-5-78147, the preferred range of the total iron oxide in terms of Fe2O3 is about 0.6-0.64%. In this case, a visible light transmission is at most about 71%, and thus it cannot say that the visible light transmission is sufficiently high.
The infrared and ultraviolet radiation absorbing glass disclosed in the above-described JP-A-6-56466 includes an infrared and ultraviolet radiation absorbing glass having relatively high visible light transmission. However, in order to obtain high total solar energy absorbing power, an amount of divalent iron in terms of Fe2O3 is 30-40% by weight based on the weight of the total iron in terms of Fe2O3. As a result, melting under stronger reducing condition than the general is required. Further, the total cerium in terms of CeO2 is 0.5-0.8%, which is relatively large. This results in making it difficult to conduct melting under strong reducing condition, and also increases raw material cost.
The present invention has been made in view of the above-described problems in the prior art.
Accordingly, an object of the present invention is to provide an infrared and ultraviolet radiation absorbing glass having green tint, and in particular an infrared and ultraviolet radiation absorbing glass having high transmission and pale bluish green tint which is suitable for use as a glass for automobiles or a glass for construction.
According to the present invention, there is provided an infrared and ultraviolet radiation absorbing glass comprising, in % by weight:
a soda-lime-silica basic glass, and
coloring components comprising
0.40 to less than 0.58% total iron oxide (Txe2x80x94Fe2O3) in terms of Fe2O3,
0.05 to less than 0.5% CeO2,
0 to 0.5% TiO2, and
0.0001 to 0.002% CoO,
wherein 20 to less than 30% of Txe2x80x94Fe2O3 is FeO in terms of Fe2O3.
The content of TiO2 is preferably 0 to less than 0.2%, more preferably 0 to less than 0.1%.
The infrared and ultraviolet radiation absorbing glass composition preferably further comprises 200 ppm or less of MnO.
The infrared and ultraviolet radiation absorbing glass preferably has, when the glass has a thickness of 3.25 to 6.25 mm, optical characteristics such that a visible light transmission measured with CIE standard illuminant A at a wavelength region of 380 to 770 nm is 75% or more, a dominant wavelength measured with CIE standard illuminant C at a wavelength region of 380 to 770 nm is 490 to 515 nm, a total solar energy transmission measured at a wavelength region of 300 to 2,100 nm is less than 55%, and an ultraviolet transmission defined by ISO 9050 is less than 20%.
The reason for limitations of the glass composition of the infrared and ultraviolet radiation absorbing glass according to the present invention are described below. Unless otherwise indicated, all % are by weight.
The soda-lime-silica basic glass used herein means a general float composition, but may be a composition for thin plate in which contents of SiO2, alkali oxides and alkaline earth oxides are increased or decreased to increase a coefficient of thermal expansion or Young""s modulus of a glass, thereby facilitating thermal tempering, and a composition in which absorption position of coloring components is changed.
The iron oxide is present in a glass in the form of Fe2O3 and FeO. Fe2O3 is a component to enhance the ultraviolet absorbing power together with CeO2 and TiO2, and FeO is a component to enhance the absorption power of solar heat rays.
In order to obtain desired visible light transmission and total solar energy absorbing power, the content of the total iron oxide (Txe2x80x94Fe2O3) must be in a range of 0.40 to less than 0.58%, and the proportion of FeO to Txe2x80x94Fe2O3 (the amount of FeO is generally a value in terms of Fe2O3) must be in a range of 20 to less than 30%. If the total iron content and the proportion of FeO to Txe2x80x94Fe2O3 are lower than the respective lower limit of the above ranges, the total solar energy absorbing power becomes insufficient, and on the other hand, if those are higher than the respective upper limit of the above ranges, the visible light transmission becomes too low.
In order to obtain a desired ultraviolet absorbing effect in such total iron oxide content and proportion of FeO to Txe2x80x94Fe2O3, the CeO2 content must be within a range of 0.05 to less than 0.5%. If the CeO2 content is less than 0.05%, the ultraviolet absorbing effect is not sufficient, and on the other hand, if it is 0.5% or more, absorption of visible light at a short wavelength side is too large, so that a desired color tint is not obtained and also cost of raw materials increases.
TiO2 is not an essential component, but can be added in an appropriate amount such that the optical characteristics intended in the present invention are not impaired, in order to increase the ultraviolet absorbing power of a glass. If the TiO2 content is too large, a glass tends to color yellow. For this reason, the upper limit of the TiO2 content is generally 0.5%, preferably less than 0.2%, and more preferably less than 0.1%.
CoO, although in a slight content, is an essential component, which is important to prevent the color tint from being yellowed in the case of containing iron oxide and cerium oxide together, and to adjust color tint of a glass to a preferable bluish green. The CoO content is usually 0.0001 to 0.002%.
MnO is not an essential component, but is a component effective to adjust color tint of a glass in the case of containing iron oxide and cerium oxide together, and the proportion of FeO to Txe2x80x94Fe2O3. If the MnO content increases, coloration by itself affects a glass. For this reason, the upper limit of the MnO content is 200 ppm.
SnO2 may be added as a reducing agent to the glass having the above-described components, in an amount of up to 1%. Further, at least one of Cr2O3, NiO, V2O5, MoO3 and the like may be added as a coloring agent as conventional in an amount such that the objective pale green color tint in the present invention is not impaired. The coloring agents may be added simultaneously.